A series of posts on software for identifying file formats. Identifying a file means at least identifying its type, and possibly the subtype and determining if the file really is the type it claims to be. There are a variety of ways to identify the the file, and there are problems associated with these ways. Some files can belong to more than one type. Knowing the version and subtype of a file can be important. And knowing the subtypes can indicate whether or not a file is suitable for archiving.
In Linux or Unix the file command can be used to check the file, its identifiers, character encoding, and possibly the language of a text file. The basic syntax is
file --mime filename.